Interpretivists seek to provide an explanatory account of shared practices (that is, the international legal order) by rationally reconstructing the motivations of participants within such practices. The international legal theories of Weil, Oppenheim and the Policy Science School apply an interpretive method, similar to Weber’s, to the study of international law. Dworkin’s general legal theory, called ‘constructive interpretation’, was considered in relation to international law in his final work. Lauterpacht’s ‘progressive interpretation’, developed in the 1930s, offers a philosophy of international law which is very similar to that of Dworkin. These approaches are set out and explored in what follows. Moreover, it is suggested that interpretivist method was explored and endorsed in international law (many years before it was developed in general legal theory) because it offered a plausible and robust method by which a single international legal order could be forged from disparate fragments of international and diplomatic practice.